The invention relates to an easily tearable film which may be suitably used as cover material of a press through pack (hereinafter referred to as xe2x80x9cPTPxe2x80x9d) and a blister pack in the field of pharmaceuticals and foods.
Aluminum foil (hereinafter referred to as xe2x80x9cAl foilxe2x80x9d) which is excellent in easy-tear properties, gas barrier properties and resistance to vapor permeability is conventionally used as cover material of a PTP and a blister pack in the field of pharmaceuticals and foods.
Blister sheets prepared by vacuum forming of a monolayer sheet or a multilayer laminated sheet made of plastics, such as polyvinyl chloride (PVC), polypropylene (PP), polyvinylidene chloride (PVDC), polyester (PET), cyclic olefin copolymer (COC) and polyethylene (PE) are used as base material.
However, Al foil as cover material tends to remain without incineration thereof when thermal disposal of a used PTP on which Al foil is adhered as waste product is conducted. Incineration of Al foil until ashing requires considerably high temperature. Incineration at such a high temperature damages an incinerator leading to a short lifetime thereof. Fractional recovery of Al foil separated from base material requires a great amount of manpower and is substantially impossible.
In addition, wastes comprising packaging containers for drugs such as a PTP from medical institutions (hospital, etc.) have a problem of environmental pollution so that hospitals are requested to dispose of the wastes by themselves or to entrust the wastes to waste-disposal companies.
Thus, cover material of a PTP and a blister pack is requested to be made of materials capable of incineration in the same condition of temperature at which an incinerator is not damaged as base material of a PTP and a blister pack.
Under such circumstances, a variety of plastics and papers are now used as cover material of a PTP and a blister pack for pharmaceuticals and foods in place of Al foil. For example, cover material consisting of plastic film whose easy-tear property is imparted by adding a great amount of mineral filler to a plastic resin so as to reduce film strength thereof, or cover material consisting of plastic film whose easy-tear property is imparted by utilizing orientation of the film caused by stretching the film in at least one direction with a high stretch ratio is used. Alternatively, cover material made of papers such as glassine paper is partially used.
Cover material blended with a great amount of the filler has, however, a problem that mineral filler is scattered when the cover is torn for unsealing, leading to contamination of drugs or adhesion of the filler to foods. The cover material consisting of the above-mentioned film whose easy-tear property is imparted by utilizing orientation of the stretched film has a drawback that a directional property of the film makes it difficult to take out some packaged products. Furthermore, the cover material made of glassine paper is remarkably poor in resistance to water vapor permeability.
The present invention is conducted under such circumstances. It is an object of the invention to provide an easily tearable film which is comparable to Al foil in an easy-tear property and excellent in gas barrier property and resistance to water vapor permeability with no possibility of damaging an incinerator during thermal disposal. It is another object of the invention to provide an easily tearable film which is suitable as a cover material of a PTP, a blister pack, etc.